Process for preparing para-(n-secalkylamino) phenols



Patented Feb. 5, 1935 UNITED STATES PATENT OFFICE Randolph '1. Major, Plainfield, N. J., assignor to Merck & Cd, inc, Rahway, N. J., a corporatier. of New Jersey No Drawing.

Original application March 23,

1931, Serial No. 524,765. Divided and this application January 2'7, 1934, Serial No. 708,693

7 Claims.

This is a division of my application Serial No. 524,765, filed March 23, 1931, for Process for preparing para-(N-sec-alkylamino-) phenols and other substituted phenols and their salts.

My present invention relates to the manufacture of certain new para-(N-sec-alkylamino) phenols and other substituted phenols and their salts used. largely as photographic developers and fur dyes, and to improvements in processes of making these groups of compounds generally.

Para-isopropylamino-phenol has been prepared by Buc, U. S. Patent No. 1,555,452, September 29, 1925, by the interaction of isopropyl chloride and p-aminophenol.

I have found that the preparation of para- (N-sec-alkylamino) phenols in general may conveniently and relatively cheaply be obtained in very pure form by the reduction of p-nitro-phenols in solution in dialkyl ketones (with or without the presence of an inert polar solvent such as alcohol) by hydrogen in the presence of a suitable hydrogenation catalyst such as platinum, palladium, or nickel, the last under 50 atmospheres pressure at 100 C. as described by Komat- Sn and Amatatsu, Mem. Coll. Sci. Kyoto Imp. Uni, Ser. A. 13,329 (1930); C. A. 25,500 (1931).

In the process thus carried out, para-aminophenol is also concurrently formed and appears as an impurity which can, however, be readily removed from the alkylamino-phenol by combining the aminophenol with aldehydes according to known methods. A convenient method for accomplishing the separation of the aminophenol is as follows:

An aqueous solution of the mixture of palkylamino-phenol and p-aminophenol in a weak acid is shaken with an aromatic aldehyde. The condensation product between the aldehyde and the p-aminophenol is removed. Excess of the aidehyde is removed by heat or an inert solvent. The

remaining solution contains the salt of the purified p-alkylamino-phenol. The free base may be obtained by means of alkalies.

These alkylamino-phenol preparations after purification may readily be converted into soluble salts, for example, the sulphuric acid addition salt or hydrochloride. These salts of p-(N-sec-alkylamino) phenols are white, crystalline compounds, readily soluble in water and are highly desirable for use as photographic developers and for hair dyes.

The following examples will illustrate a preferred method of applying my invention:

Example I.--25.2 grams of p-nitrophenol is dissolved in an excess of acetone at room temperature. To this solution is then added 0.2 of a; gram of a platinum catalyst prepared preferably according to the method of Adams and Shriner, J. Am. Chem. Soc, 45, 2171 (1923) The mixture is shaken in an atmosphere of hydrogen at room temperature until the calculated amount of hydrogen has been absorbed. After the catalyst has been filtered off, the residue of acetone is distilled ofi in vacuo. The remaining material is then dissolved in dilute acetic acid. More than sufficient benzaldehyde is then added to combine with all the p-amino-phenol formed during the reaction period. The mixture is vigorously shaken for half an hour. This is then extracted with ether. The aqueous layer is made neutral with sodium carbonate. The p- (N-iso-propylamino) phenol which precipitates out is filtered off, and recrystallized from benzene. t is obtained in the form of white, needle-like crystals, soluble in dilute acids and alkalies, and in ether and alcohol, and insoluble in water, having a meltin point of 156 0.

Example II.12.3 grams of para-nitrophenol is added to a solution 14.6 grams of methyl ethyl ketone and 20 cubic centimeters of methyl alcohol. To this solution is then added 0.2 grams of platinum catalyst as in Example 1. After the mixture has been shaken in an atmosphere of hydrogen and has absorbed the required amount of hydrogen, it is treated in the same way as described in Example I for the preparation of the p-iso-propylamino phenol, except that the p-(N-sec-butyl-amino) phenol, thus obtained in this process, is recrystallized from toluene, the butyl compound is in the form of white crystals soluble in acids and alkalies, alcohol, and ether, and insoluble in water, and has a melting point of 118-119 C. Its hydrochloride is soluble in water, insoluble in ether, decomposes without melting when heated.

Example III .l2.3 grams of para-nitrosophenol is dissolved in acetone at room temperature. To this solution is then added 0.2 gram of the platinum catalyst mentioned in Example I. After the mixture has absorbed the required amount of hydrogen it is treated in the same way as was described in Example I. The paraisopropyl-aminophenol melts at 155l56 C.

In the foregoing examples my method has been shown with the use of para-nitrosophenol and para-nitrophenol, but I am not limited to these precise forms, but may use quite satisfactorily in their place suitable carbon substituted derivatives of these.

Having thus set forth the manner and means of carrying out this invention, I request the iss'uance of Letters Patent on the following claims:

1. The process of nf aking p-(N-isopropylamino) phenol comprising the addition of paranitroso-phenol to acetone at roohi temperature, addingTa hydr gehatiOI'ii catalyst; shaking the mixture "in an atmosphere of hydrogen until the required amount of hydrogen has been taken up; filtering 01f the catalyst and distilling 'off the residue of acetone in vacuo; dissolving the remaining material in dilute acetic acidjfadding more than suffieient benzaldehyde to comloine with all the arriino-phenol for-med during'itlie reaction period; shaking the 'i'ni'x'tuie and"there-; after extracting with ether; neutralizing the; "aqueousflayer resulting with sodium carbonat 1 and theft filtering off theformed"p (N-isopropyl amino) phenol and recrystallizing the' "same-from benzene: J

1 2. In a process of making p-(N-see-alkylammo P en s the tep9? r d c n -r tro i ieeqls n the te c dialkylk q es.

; of platinum as a catalyst.

3. In a process ofimaking p-(N-sec-alkylamino) phenols, the step of reducing p-nitrosophenols in the presence of dialkyl ketones with the aid of a hydrogenation catalyst.

4. In a process of making fp-(Nesec -alkylamino) phenolts, the step of reducing p-nitrosophenols in the;presence of dialkyl ketoneswith the aid of platinum 'as a catalyst. I

5. In a process of making p-(N-isopropylaminol phenol, the step of reducing p-nitroso= phenom in the presence of acetone. 7 6.1 11 a process of making p-(N-isopropyl amino} phenol, the step of reducing p-nitrosophenols in the presence of acetone with the aid of a hydrogenation catalyst. 5i

'7. In a process of making p-(N-isopropylamino) phenols, the step of reducing pi-nitrosophenols in the presence of acetone with the aid RANDOIEH MAJOR. 

